Does the data quality of nacelle-based scanning lidar measurements deteriorate after passing through an offshore wind farm?

Scanning lidars are increasingly favored for wake measurements because of their ability to scan over and therewith assess the wake effects of single wind turbines and greater parts of farms. While these effects are often studied only qualitatively, this study quantitatively evaluates the accuracy of scanning lidar measurements in an offshore campaign that involved three long-range scanning lidars installed on turbine nacelles for farm-scale wake measurements. We investigated measurements from two scanning lidars positioned at the front and back of the wind farm during a westerly wind case study. The lidar data underwent quality control and post-processing to account for nacelle motion. An interpolation scheme aligned the measurements from both systems onto a common grid for comparison. The results reveal an MBE = 0.17 ms-1, an RMSE = 0.71 ms-1, and an R2 = 0.93 between the two lidars. The accuracy of the nacelle setup is assessed using bin standard error, with a maximum value of 1.11 ms-1 found. We identify and discuss controllable sources of error such as motion compensation and interpolation effects, as well as non-controllable sources of error including turbulence and signal quality.